Lygus control starts beyond orchard

Bug's environment outside crop should be monitored Lygus populations will produce inside orchards. However, external populations of lygus are the primary source of infestations and therefore are extremely important in any monitoring and control program.

I work with pears and apples and have learned that it is critical to know the environments surrounding orchards, especially borders and levees, if you are to be successful preventing lygus damage. My procedure is to take 25 to 100 sweeps of groundcovers in three different areas, inside the orchard, along its perimeter and adjacent environs.

Sampling begins in the spring in groundcovers after the fruit is formed. A sweep net is the most efficient way to evaluate lygus populations. Sweep orchard perimeters first and be especially vigilant during protracted heat waves when lygus tend to move into the trees.

After fruit is formed, sample 100 fruit samples, again sample first along orchard borders or adjacent, known hot spots.

The economic thresholds are not clearly defined in western pome fruit. Under University of California Integrated Pest Management guidelines, in 100 fruit samples, one of more damaged fruits may require treatment. When sweeping, the practice I use is one lygus per sweep in 25 to 100 sweep samples as a threshold level.

Pesticides used to control lygus include:

Dimethoate - Most widely used for both knockdown and residual control. However, is disruptive to natural enemies. I do not recommend using it throughout the entire orchard, but rather use it to control hot spots, on groundcovers or along orchard perimeters.

Carzol (formetanate huydrochloride) - A good knockdown material, but again highly disruptive to natural enemies.

Thiodan (endosulfan) - Highly effective, but use is very restricted in California. Typically, it cannot be used.

Other registered pesticides not commonly used but available:

Diazinon - Not used for true bug control as more effective materials are available.

Oxamyl - This carbamate has not been extensively tested against true bug pests in orchards.

Esfenvalerate and Permethrin - These pyrethroids are effective against lygus, but are not used in Western pears and apples since they are highly toxic to predatory mites and their use may result in outbreaks of spider mites.

Imidacloprid - This new neo-nicatinoid insecticide may have significant activity against the true bug complex, but further testing is needed.

Cultural and biological options available include treating borders first if lygus numbers are found in potentially damaging numbers.

Weed control or vegetation management can be another effective cultural control of lygus, and finally traps crops can be used to attract and control lygus.

The key to lygus control is to remain vigilant for potentially damaging buildups of lygus and integrate multiple tactics to manage the pest on the outside of the orchard rather than allowing it to become established inside the trees.

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